In the prior art, a ski boot is generally composed of a rigid shell, obtained by injection molding a plastic in a manufacturing mold, to which is attached a hinged plastic cuff, similarly obtained by injection molding and designed to cover the lower part of the leg. This assembly forms a ski boot upper made of plastic with a hardness of generally between 40 and 60 Shore D. The method of injection molding the shell and cuff requires very expensive manufacturing molds. The shell is designed to enclose the foot and corresponds to a given boot size. It comprises a rigid outer bootboard comprising standardized front and rear lips designed to engage with the jaws of a toepiece and a heelpiece, respectively, of a device for binding the boot to the ski. A “Zeppa” bootboard is generally built into the shell, followed by a comfort innerboot which usually contains an insole. It is known practice to provide a shell of a different size for each integer boot size—that is, the length of its bootboard, between the two lips, is different, and its overall dimensions are different to correspond to feet of different sizes, in accordance with standardized volumes according to the Mondopoint standard, for example. These shells therefore require a different manufacturing mold for each boot size. Next, it is known practice to provide two different half boot sizes for each shell by allowing two innerboots of slightly different volumes to be inserted or having two insoles of different thicknesses in the same shell, thus increasing the number of options for the skier. Next, the distance between the toepiece and heelpiece of the ski boot binding device is adjusted to the size of the outer bootboard of the ski boot for actual skiing.
This is a burdensome situation for the management of ski boots and skis, especially for ski equipment hire stores, which have to keep multiple series of ski boots in all sizes so that they can offer customers the right ski boot for their size. Next, when a customer has selected a boot, he or she needs a ski to fit: the heel-to-toe separation of the selected ski binding device rarely corresponds to the selected ski boot, because the previous hirer of the ski often had a different size of boot, which means the separation must be adjusted to fit it to the selected ski boot. Ski equipment hire stores thus have to undertake many adjustment operations, which takes up time and can lead to mistakes. They must also offer a series of boots in all integer and half sizes, which is a heavy investment.
To ameliorate this situation, document US2008196275 proposes a solution in which a series of boots extending from size 23 to size 34 uses only three different bootboards, that is to say three different lengths requiring only three different corresponding spacings between the front toepiece and the heelpiece of a device for binding a boot to a snowboard. This solution is therefore advantageous in that it greatly reduces the demands and the risk of error in setting up the ski boot binding device. To achieve this advantageous result, the solution proposes two boot shells of different sizes for each length of bootboard, making a total of six different shells. Each of these shells is then given two innerboots of different dimensions to produce two different boot sizes, which is how the desired twelve different boot sizes is achieved. The problem with this solution is that it requires six different manufacturing molds to produce the six different sizes of shells, so it is still expensive to purchase the complete series of boots. Also, innerboots compensate for the volumes of the shells to form two different sizes out of each boot shell: these inner boots must therefore have thick walls to form the small sizes, which is detrimental to the transmission of forces from the foot to the ski and reduces the overall performance of the boot.
Document EP1952711 proposes an alternative solution by a similar approach in which a series of boots can be used to create twelve boot sizes from four different bootboard lengths, and three different shells for each length of bootboard. This solution suffers from the same problem as the previous solution because it inevitably requires twelve different molds to produce twelve different shells.
Consequently, the prior art solutions allow the number of possible combinations of bootboard length to be reduced in order to reduce the necessary adjustments of the ski boot binding devices. However, they still require a heavy investment for the purchase of the complete series of boots to cover all boot sizes.
There is therefore a need for another solution that reduces the investment cost of obtaining a series of ski boots.